On the Development of Tragophylloceras loscombi (J. Sowerby)

Publisher Website
Google Scholar
Abstract
I. Introduction. As is well known, few localities are so productive of well-preserved Liassic ammonites as the cliffs at Lyme Regis and Charmouth. They have furnished a considerable proportion of the types of Lower Liassic ammonites created nearly a century ago in ‘The Mineral Conchology of Great Britain,’ and one of these types, fortunately one of those the figures of which were good enough to allow of correct interpretation by later authors, is Ammonites loscombi J. Sowerby (1817). During a prolonged investigation of the Liassic succession at Charmouth, Mr. W. D. Lang (1913) has collected abundant fossil material with particular reference to its exact stratigraphical horizon, and I am indebted to him for permission to study the ammonites. In this material, Tragophylloceras loscombi is represented by hundreds of specimens (chiefly young), and a study of the ontogeny of that interesting ammonite forms the basis of the present paper. The bearing of certain important facts brought out in this study upon the phylogeny of the genus Tragophylloceras , and the speculations on the connexion of the latter with allied lineages, will prove, it is hoped, of general interest. Sowerby stated that his ammonite came from the ‘Blue Lias,’ but gave no further details. The type-specimen, which is preserved in the British Museum (Geological Department, No. 33425), shows the bluish limestone-matrix, iridescent pearly layer, and general mode of preservation of the specimen figured by Wright (1880) (B.M. C 2205) and stated to be a ‘very characteristic fossil of the “Green Ammonite Bed,” Middle

This publication has 3 references indexed in Scilit: